Animal fats and heart disease: saturated with misinformation

As a species, our ability to quickly and effectively respond to public health crises and epidemics is crucial to our survival. From the Plague of Athens in 429 BC and the “Black Death” of 14th century Europe, all the way to the recent outbreaks of Ebola in Africa, our history is pockmarked with grim battles against illness. But what happens when the strategies we adopt turn out to be counter-productive? What happens when we are wrong?

While we may now laugh at the thought of doctors wearing herb-filled masks to ward away the bubonic plague, or ancient Chinese emperors drinking mercury to obtain immortality, thinking ourselves immune from such folly is dangerous. You only have to look at our response to the burgeoning American heart disease epidemic of the 1950s, and how it characterised a half-century of nutritional advice about fat, to realise that, even today, good science doesn’t always triumph.

A disheartening health crisis

Since the 1930s, cardiac morbidity had been steadily increasing in United States, and, in only a few decades, had grown to become a major public health issue. When the then-president, Dwight Eisenhower, suffered his own heart attack in 1955, it seemed there was a clear danger of America’s population spiralling into a pathologically unhealthy morass. As cardiac morbidity increased, so too did the anxiety of medical professionals and health officials. Studies were commissioned, reports requested, and decrees made; something had to be done, and fast.

One figure that was central to our response to this cardiac crisis was Ancel Keys, a researcher from the University of Minnesota. Keys believed that health outcomes were inextricably linked to diet, and set out to prove this by gathering data from across the globe. His findings, particularly those in the Seven Countries Study first published in 1970, seemed to show that consumption of fat, particularly animal fats, had a distinct correlation with incidence of heart disease, and that limiting its intake could markedly improve lifespan and quality.

Though his contributions to medical science earned him a position on the nutrition committee of the American Heart Association (AHA) and even a space on the cover of Time magazine, Keys would also spearhead one of the most misconceived public health campaigns in recent history.

Why Ancel Keys was wrong about fat

Keys’ Seven Countries Study was the most comprehensive of its kind, involving nearly 13,000 male participants in America, Japan, and Europe. Its goal was to investigate how diet and health interacted, and from that, beneficially inform successive generations of public health policy across the globe. Unfortunately, it also was fundamentally flawed.

There is significant evidence that Keys cherry-picked the countries whose data he would include. Yugoslavia, Finland and Italy were in, but France, Switzerland, Sweden, and West Germany, where heart disease rates were low despite high-fat diets, were out. Keys’ findings in Crete, from which the concept of the much-lionised “Mediterranean diet” emerged, were equally disputable. A paper, only released in 2002, revealed that Keys had visited Crete during a period of particular hardship following World War II, and taken many of his measurements during Lent, meaning that a majority of the population was consuming significantly less animal fat than usual. In fact, only a few years earlier, epidemiologist Leland G. Allbaugh had also studied the Cretans and found that while their diet seemed healthy, they were constantly hungry and craved animal products such as meat and cheese.

While many scientists were quick to raise questions about Keys’ conclusions, and continue to do so, further studies seemed to confirm his findings. Although many had severe methodological flaws, such as not accounting for tobacco use or inadequately monitoring participants, governments and health organisations quickly began rolling out recommendations that people drastically limit the amount of fat in their diets. President Eisenhower found himself trading his breakfast of eggs for a bowl of cereal.

In 1961, as part of the AHA’s nutrition committee, Keys was involved in creating the country’s first ever dietary guidelines that directly targeted animal fats, with the U.S. Department of Agriculture following suit in 1980. The chips were down, and so was butter, milk, red meat, and cheese consumption across the globe; the anti-fat crusade was adopted as the central tenet of the scientific narrative around diet and health, where it would stay for the next half a century.

What happened when we gave up animal fat

One immediate consequence of this upsurge in concern about dietary fat was, unsurprisingly, that people started to consume a lot less of it. While quality data is sparse, since the early 1970s, America has seen a drop of about 11% in fat consumption. This gap had to be filled by something, and stodgy carbohydrates such as pasta, grain, and vegetables like potatoes were the natural answer — over the same period, our consumption of them grew by 25%.

The second consequence of the shift away from animal fats was the increasing presence of vegetable oil in the food we eat. The fatty products Americans once consumed were swiftly replaced by low-fat alternatives that usually relied on additives to replicate the texture and taste of their predecessors. Vegetable oil, in particular, was a big winner from this shift; along with the sugar industry, vegetable oil manufacturers had provided significant financial assistance to the fledgling AHA. Now, these oils, barely present in our diet in 1900, represent between 7% and 8% of our entire caloric intake in America — the biggest increase in consumption of any item in our diets over the past century.

While at the time, these ground-breaking changes to how we approached food were hailed as lifesaving, current, and even decades-old, research indicates that they may have been damaging instead. The shift from animals fats to vegetable oils and carbohydrates has, in fact, had dramatic consequences for health that are only being fully measured now.

Did less fat in our diets actually make us less fat?

If the purpose of reducing animal fat in our diet was to reduce obesity, it has profoundly failed as a strategy. This graph, produced by the US National Center for Health Statistics clearly demonstrates that American obesity rates have grown hugely since the 1970s when public health bodies first started to promote sugar over fat.

Also clearly evident is the dramatic increase in diabetes diagnoses, which, if anything, has only accelerated in recent years. This can be directly linked to increases in carbohydrate consumption. Carbohydrates, when broken down by the body into glucose, cause spikes in blood sugar, promoting the release of insulin. Too many spikes over too long a period, and diabetes risk increases swiftly.

It’s important to note, and this may surprise you, that it doesn’t really matter what sort of carbohydrates you consume either. While there are many reasons to avoid processed carbohydrates in favour of whole grains, both are equally capable of causing weight gain and associated health issues.

Women’s health has particularly suffered from the move away from animal fats, and numerous studies have shown that high total cholesterol levels in women are actually associated with longer, rather than shorter, lifespan. While this was conclusively shown in the famous Framingham study in 1971, it was neglected from inclusion in the final report. Nor was it considered in general recommendations on fat intake to the American public, all of which were based on data drawn from male, middle-aged populations.

Some would argue that these guidelines have actually increased heart attack risk for women; despite statistics that indicate diets richer in fruits, vegetables, and grains, they now experience higher obesity rates than men and their risk of cardiac mortality is now virtually identical.

The problem with hydrogenated oils

Equally as worrying as the growth in obesity and diabetes are the health implications of our increased reliance on vegetable oils, both as a cooking medium and as a food additive. Even in the 1970s and 80s, clinical trials found that those who had diets high in vegetable oils were found to suffer higher rates of cancer and gallstones, and were even more likely to die from violent accident or suicide.

Studies going back to the 1940s have also shown that heated vegetable oils are high in oxidation products that could potentially cause cirrhosis of the liver, a particular concern in restaurants where food is fried in oil that has been repeatedly heated and cooled. This danger was thought to have been mitigated by hydrogenating the oils, using a catalyst to convert them from liquid to solid, but this may have instead created other health problems. Hydrogenated oils, the chemical foundation of many mass-produced cakes, biscuits, chips, breads, frostings, frozen and fried food, and innumerable other products, are high in trans fats, recently condemned by the Food and Drug Administration (FDA) for their capacity to raise LDL or “bad” cholesterol and their implication in interfering with basic cell function.

Were animal fats even bad for us after all?

Sadly, it’s only recently that mainstream media have caught up with decades-old science and reported that animal fats are not as bad as first thought. In fact, a recently published meta-analysis of current research found that many studies have historically shown that saturated fat consumption is not strongly associated with poor cardiac health. While, clearly, this should not be taken as an encouragement to overindulge on butter, bacon, and cheese, it shows that nutrition is never as simple as it seems, and that getting it wrong can be just as damaging as doing nothing.

References

Health, United States, 2008: with special feature on health of young adults. National Center for Health Statistics (US). Hyattsville (MD): National Center for Health Statistics (US); 2009 Mar. Chartbook.

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